Threema backup error due to missing interface

Hi guys,

I want to backup my Threema data, because I want to make an upgrade to Android 11 on my Fairphone 3.
When I start the backup process, the following error message appears:
“Your device is missing an activity for Intent.ACTION_OPEN_DOCUMENT_TREE”

I contacted the Threema support and they said, that this is an problem with the operating system (missing interface) and I should contact you.

Is this a known issue?

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